NoteHKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
| Data type | Range | Default value |
|---|---|---|
| REG_DWORD | 0 - 255 retransmission attempts | 2 |
Determines how many times TCP retransmits an unanswered SYN-ACK (connection request acknowledgement). TCP retransmits acknowledgements until they are answered, or until this value expires. This entry is designed to minimize the effect of SYN flooding on the server.
This entry also determines, in part, whether the SYN attack protection feature of TCP is enabled. This feature detects symptoms of SYN flooding and responds by reducing the time server spends on connection requests that it cannot acknowledge. SYN attack protection is enabled when the value of SynAttackProtect is 1 and the value of this entry is at least 2.
TCP/IP adjusts the frequency of retransmissions over time. The delay between the first and second retransmissions is 3 seconds. This delay is doubled after each attempt. After the final attempt, TCP/IP waits for an interval equal to double the last delay and then closes the connection request.
Note
Windows 2000 does not add this entry to the registry. You can add it by editing the registry or by using a program that edits the registry.
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